SilentLou
06-05-2008, 09:22 PM
The past couple days have been summer like, getting hot and humid. Yesterday, with intake temp. around 80F, on the highway I noticed a major loss of power and much lower than normal mpg (lowest I've ever seen on the car) per the scangauge, especially going uphill. I actually found that downshifting to 4th at 3K RPM got better mpg than ~2K RPM in 5th gear, which is very unusual. After 10-15 minutes, things returned to normal, not sure what triggered it.
Today, it was hotter and more humid, intake temp. about 95-100F. Initially I was getting good mpg, better than normal. Once I got on the same stretch of highway pointed out above from yesterday, I felt that same loss of power and low mpg, very noticable. I again downshifted to 4th and from that point on, things were back to normal. In fact, from that point on, I got my best mpg ever (got about 57mpg).
Car is a 99 Honda Civic HX. I know it's already a lean burner and apparently it switches to an even leaner (too lean) burner under certain conditions. I don't understand exactly what triggers this super lean mode, it can't be temperature alone because I've now seen it trigger at roughly 80F temp. and also at >95F (also noticed this when I had the WAI connected, which is now removed). Maybe it is a combination of temperature and mass airflow, I can't think of any other factor. Also puzzling is what triggers it to get out of super lean mode. Any ideas?
Today, it was hotter and more humid, intake temp. about 95-100F. Initially I was getting good mpg, better than normal. Once I got on the same stretch of highway pointed out above from yesterday, I felt that same loss of power and low mpg, very noticable. I again downshifted to 4th and from that point on, things were back to normal. In fact, from that point on, I got my best mpg ever (got about 57mpg).
Car is a 99 Honda Civic HX. I know it's already a lean burner and apparently it switches to an even leaner (too lean) burner under certain conditions. I don't understand exactly what triggers this super lean mode, it can't be temperature alone because I've now seen it trigger at roughly 80F temp. and also at >95F (also noticed this when I had the WAI connected, which is now removed). Maybe it is a combination of temperature and mass airflow, I can't think of any other factor. Also puzzling is what triggers it to get out of super lean mode. Any ideas?